US homeland security strategy is undergoing renewed scrutiny amid escalating tensions with Iran, particularly in 2025. Intelligence assessments warn of sleeper cells covert operatives or sympathizers embedded within the United States as growing vectors of risk. The Iranian government, facing pressure from sanctions and regional isolation, is accused of expanding its asymmetric playbook to include low-visibility threats across US soil.
Following targeted US strikes on Iranian nuclear facilities and militias in 2024, Iran’s retaliatory posture has sharpened. Department of Homeland Security (DHS) bulletins now regularly refer to an “elevated threat environment,” flagging sleeper cells as a credible component of Tehran’s overseas retaliation strategy. The 2025 Homeland Threat Assessment names Iran as the primary state sponsor of terrorism and outlines its deliberate cultivation of foreign networks including potential assets within US borders.
Rising Numbers And New Patterns
US Customs and Border Protection data show that more than 1,750 Iranian nationals illegally entered the country between February 2021 and November 2024. This marks a twenty-fold increase compared to the preceding seven-year period. Additionally, over 7,000 Iranian nationals were declared inadmissible at official ports of entry. In response, Immigration and Customs Enforcement (ICE) has launched focused operations, arresting more than 130 individuals flagged as potential security risks since mid-2025. These trends have prompted a significant policy conversation around screening, vetting, and national readiness for nontraditional threats.
Sleeper Cell Mechanics And Activation
Sleeper cells are structured to operate beneath the surface of society. Agents often assimilate quietly into communities, living for months or years without visible activity, until receiving activation orders. The potential triggers may include geopolitical events, religious edicts, or specific losses to Iranian leadership.
The DHS terrorism bulletin issued in June 2025 warned of increased chances of violence if Tehran were to issue religious rulings calling for attacks. Since then federal law enforcement has discovered Iranian based surveillance targeting transport centers and synagogues, student groups, and energy infrastructure. These strategies indicate a two-fold purpose, disruptive strategies and psychological pressure.
Embedded Threats In Plain Sight
Jonathan Gilliam, an ex-FBI counterterrorism agent, warns that the sleeper cells might be lurking in plain view since they will fit perfectly well in less-policed rural regions or suburban localities. This is particularly alarming in view of the global terror patterns, such as the attacks by Hamas in October 2023 and the local attacks in South Asia. These instances are representative of a trend: the change of emphasis on the hard targets located in large cities and soft ones in less fortified areas.
Proxies, Lone Offenders, And Hybrid Plots
Iran’s operational strategy does not rely solely on state operatives. Proxy groups like Hezbollah and Hamas serve as force multipliers, capable of both planning and inspiring action abroad. These organizations are believed to maintain informal links with diaspora networks and religious institutions, offering ideological backing to individuals already within US territory.
Lone actors, self-motivated and difficult to detect are also emerging as a central concern. These individuals may not be formally trained but consume radical propaganda online or via encrypted communication channels. The Office of the Director of National Intelligence in 2025 reiterated that Iran’s intention to harm current or former US officials remains “persistent and active,” especially those linked to the killing of IRGC commander Qassem Soleimani in 2020.
Varying Degrees Of Sophistication
While Iran is capable of deploying highly trained agents, many plots involve non-professional participants. Former Defense Secretary Leon Panetta and retired General Wesley Clark have both noted the variability in skills and discipline among such actors. Investigations have uncovered attempted surveillance, failed bomb plots, and recruitment attempts within US communities—often disrupted at late stages, highlighting both the limitations and ongoing threats of these networks.
Policy, Border Controls, And Mitigation Challenges
The rise in illegal entries by Iranian nationals has ignited a national conversation about vetting and resource allocation. Congressional oversight committees are questioning the existing frameworks for monitoring “got-aways”—individuals who evade capture after crossing the border. DHS estimates that nearly 1.9 million such cases have occurred over the past few years, with limited tracking mechanisms in place.
This uncertainty complicates threat assessment and leaves US authorities vulnerable to intelligence blind spots. In the event of a sudden escalation with Iran, these gaps could be exploited by sleeper cells aiming to disrupt infrastructure, instill fear, or undermine confidence in national security.
Reinforcing Detection And Coordination
While the US has successfully intercepted Iranian-backed plots over the past five years, experts caution that the nature of future attacks may evolve. “Hybrid” operations could combine cyberattacks, coordinated shootings, and psychological warfare requiring enhanced interagency coordination and rapid-response protocols. The 2025 Homeland Threat Assessment calls for improved data-sharing systems, local law enforcement training, and increased monitoring of transnational digital communications.
ICE, FBI, and DHS joint task forces have been expanded in select regions with known vulnerabilities, particularly near critical energy facilities and symbolic government institutions. However, law enforcement leaders warn that budget constraints and personnel shortages continue to challenge sustained counter-sleeper cell vigilance.
Strategic Shifts And Public Awareness
US security architecture is adapting to meet the complex threats posed by Iranian networks. From biometric tracking at entry points to artificial intelligence models that detect behavioral anomalies, tools once reserved for battlefield environments are being repurposed for domestic use.
But policy alone cannot close every vulnerability. Intelligence officials stress the need for public engagement. Awareness campaigns aimed at faith institutions, schools, and transportation workers are being developed to train civilians to recognize early signs of sleeper cell behavior especially where operatives may attempt to recruit or coerce sympathizers.
Iran no longer operates on a low profile only limited to the lingo of nuclear politics or local militancy. It reveals itself on the domestic, local and day-to-day levels, requiring a society-wide response.
The knowledge of sleeper cells functioning, the influence of a geopolitical change on their functioning will play a very important role in understanding the durability of the US homeland security systems. With the threats being more decentralized and less pronounced, national preparedness is going to be based not only on policy, but also on the readiness of the collective of institutions and individuals to identify, adapt, and react in time.
